1. Field of the Invention
This invention relates to a signal recording apparatus, a signal record(recording, recordable or recorded) medium and a signal reproducing apparatus for prohibiting copying or unauthorized use.
2. Description of the Related Art
Recently, with increased capacity and coming into widespread use of digital recording media, such as optical discs, prohibition of duplication or unauthorized use thereof has become incumbent for protecting the copyright of recorded signals. That is, digital audio data or digital video data can be duplicated by copying or dubbing without deterioration, while computer data can be duplicated to give data which are the same as the original data, so that troubles are caused due to unauthorized copying.
With this in view, a pre-set ID bit for preventing unauthorized copying is occasionally recorded on an original signal record medium for prohibiting unauthorized copying.
For example, in a system for prohibiting the unauthorized copying in a digital audio data recording/reproducing apparatus termed a rotary head digital audio tape recorder (R-DAT), an inhibiting code for inhibiting digital copying or generation-serial copying, that is for generation limitation (inhibiting code of a standard of the serial copying management system or SCMS) is recorded in a main data area for digital audio signals recorded on a digital audio tape as a signal record medium, so that, when the inhibiting code is detected by the digital audio signal recording apparatus, copy recording of the digital audio signals on a new digital audio tape is inhibited.
For preventing unauthorized copying of, for example, digital audio video signals recorded on a signal record medium, an ID bit for prevention of unauthorized copying (copy generation management system or CGMS) may be recorded on an original digital record medium, as in the case of the above-mentioned system for prevention of unauthorized copying between R-DAT recording/reproducing apparatus.
In the case of the computer data, it has been practiced to cipher the file contents themselves, using the encryption key information, and to permit it to be used only by the regular registered users. This system is related with a system in which digital recording media having recorded thereon the ciphered information are distributed as a form of information circulation and the user may acquire the key information on payment for the contents he or she requires in order to decipher and use the file contents.
However, the conventional inhibiting code or the encryption key information as described above is recorded in a particular location on the record medium which corresponds to the system and which is accessed by the user, as disclosed in JP Patent Publication Kokai JP-A-5-173891 (1993). Meanwhile, the inhibiting codes or the encryption key information is also usually ciphered.
If the inhibiting code or the encryption key information is fixedly arranged at an arbitrary position from one encryption technique to another, there is a risk of loss of interchangeability. In addition, if the inhibiting code or the encryption key information is fixedly arranged, the encryption technique is fixed and becomes poor in flexibility and extendibility, while the service life of the format itself tends to be diminished.
Also the encryption key information or the inhibiting code is located at a position accessible by the user, so that it may be decoded or illicitly copied by a knowledgeable user.
It is therefore an object of the present invention to overcome the above inconvenience and to provide a signal recording apparatus and a signal record(recording , recordable or recorded) medium in which a ciphered signal corresponding to a ciphered input signal and the key storage position information specifying the encryption key information arraying position are recorded on the signal record medium.
With the signal recording apparatus and the signal record medium of the present invention, a ciphered input signal and the key storage site information specifying the arraying site for the encryption key information are recorded on a signal record medium.
With the signal reproducing apparatus of the present invention, in reproducing signals from the signal record medium of the present invention, the ciphered signal and the key storage site information are read out from the signal record medium, and the ciphered signal is deciphered using the key information stored on the site designated by the key storage site information.
Thus, by recording the key storage site information on the signal record medium for specifying the site of the key information, and taking out the key information for signal reproduction based on the key storage site information on the occasion of signal reproduction, the key information can be taken out only with considerable difficulties.
According to the present invention, since the key storage site information specifying the site of the key information is recorded on the signal record medium, and the key information is taken out on the basis of the key storage site information on the occasion of signal reproduction, it becomes possible to prohibit the unauthorized decoding or copying.